In D.C. generators the pole shoes are fastened to the pole core by
welding
counter sunk screws
rivets
brazing
counter sunk screws
A separately excited generator as compared to a self-excited generator
has all above features
is amenable to better voltage control
is more stable
has exciting current independent of load current
has all above features
According to Fleming’s right-hand rule for finding the direction of induced e.m.f. when middle finger points in the direction of induced e.m.f. forefinger will point in the direction of
none of the above
either of the above
motion of conductor
lines of force
lines of force
Iron losses in a D.C. machine are independent of variations in
speed
voltage
load
speed and voltage
load
Fleming’s right-hand rule regarding direction of induced e.m.f. correlates
magnetic flux direction of motion and the direction of e.m.f. induced
magnetic flux direction of force and direction of motion of conductor
magnetic field strength induced voltage and current
magnetic flux direction of current flow and resultant force
magnetic flux direction of motion and the direction of e.m.f. induced
While applying Fleming’s right-hand rule to And the direction of induced e.m.f. the thumb points towards
direction of motion of conductor if forefinger points along the lines of flux
direction of flux
direction of induced e.m.f.
direction of motion of the conductor if forefinger points in the direction of generated e.m.f.
direction of motion of conductor if forefinger points along the lines of flux
In D.C. generators the cause of rapid brush wear may be
imperfect contact
any of the above
severe sparking
rough commutator surface
any of the above
In lap winding the number of brushes is always
same as the number of poles
double the number of poles
half the number of poles
two
same as the number of poles
For a D.C. generator when the number of poles and the number of armature conductors is fixed then which winding will give the higher e.m.f. ?
Depends on other features of design
Either of and above
Lap winding
Wave winding
Wave winding
Copper brushes in D.C. machine are used
where high voltage and small cur-rents are involved
in both of the above cases
where low voltage and high currents are involved
in none of the above cases
where low voltage and high currents are involved
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